The current invention relates to a radial fan wheel for supplying cooling air for an electrical machine, with a number of fan blades attached along the circumference of the fan wheel that have arc-shaped blade ends, which, at their radially inner edge, enclose a first angle with a tangent to the inner circumference of the fan wheel and at their radially outer edge, enclose a second angle with a tangent to the outer circumference of the fan wheel.
In sheet metal fans, which are usually embodied as radial fans and are for supplying cooling air for electrical machines, reducing noise during operation is a continuous concern. When supplying the cooling air, among other things the turbulence noise in the vicinity of the fan blades plays a large role in the overall noise production of the fan.
In a generator, the flow of cooling air is intensely disturbed in the vicinity of the fan. The most important components that produce the turbulence are the struts and ribs of the end plate, the surface of the end plate on the side oriented toward the fan, heat sinks, and interconnection plates on the B-side of the end windings.
Important geometric parameters for the fan blades are the entry angle β1 and the exit angle β2 of the blade ends. FIG. 4 illustrates the definition of the entry angle β1 and exit angle β2 for arc-shaped blade ends 18. The entry angle β1 is defined as the angle between the radially inner edge of the blade end 18 and a tangent 22 to the inner circumference 20 of the fan wheel. The exit angle β2 is defined as the angle between the radially outer edge of the blade end 18 and a tangent 26 to the outer circumference 24 of the fan wheel. Knowing these two angles provides an unambiguous definition of an arc-shaped blade end 18 of a fan blade 16.